Subgenus Microtus, socialis species group (Zagorodnyuk, 1990). Placed in subgenus Sumeriomys by Gromov and Erbajeva (1995). Long included in M. socialis (Ellerman and Morrison-Scott, 1951; Pavlinov and Rossolimo, 1987; Pavlinov et al., 1995a). Pavlinov and Rossolimo (1998) and Kryštufek and Kefelioğlu (2002) also questioned the separate status for schidlovskii, and Pavlinov and Rossolimo (1998) placed it in the synonymy of M. socialis with reservation. Reinstated as species by Ahverdyan et al. (1991a, 1991b), who demonstrated that hybridization between schidlovskii (2n and FN = 60-62) and M. socialis (2n and FN = 62) produced only sterile F1s and analyzed supportive chromosomal and morphological data. Species status reaffirmed by Golenishchev et al. (2002) based on bacular morphology and hybridization trials. Gromov and Erbajeva (1995) listed goriensis (a replacement name for colchicus) as a subspecies.